Injection devices are generally known for the self administration of a medicament by patients. As just one example, those patients suffering from diabetes may require repeated injections of insulin. Other patients may require regular injections of other types of medicaments, such as a growth hormone. Some injection devices allow the patient to select a dose of a medicament contained within the injection device and to administer this selected dose. Setting or selecting a specified dose may be a particular problem for the elderly, the infirm, those suffering from vision difficulties and those suffering from diabetes related problems which impair their faculties.
Injection devices typically contain a medicament that may be contained in a conventional medicament container that is located within the injection device. Such conventional medicament containers, e.g. cartridges, typically comprise a bung or stopper at one end of the medicament container (i.e., the proximal end). It is this bung or stopper that is typically driven towards a second end (i.e., a distal end) of the medicament container to expel the medicament from the injection device, preferably by way of an attached double ended needle assembly.
One problem that often arises with certain conventional injection devices used for self-administration is the actual size of the injection device. For example, it is a problem that injection devices should be small or compact enough to fit into a jacket pocket or a hand bag without much difficulty. At the same time, the injection device must be of a size that enables a piston rod or a piston rod system used to drive the medicament container bung within the medicament container so that the bung can be moved both to a maximum dispense position within the medicament container and, in the case where the injection device comprises a reusable injection device, to be fully withdrawn from the medicament container to allow for replacement of the spent medicament container with a new, full medicament container.
A number of factors may affect the design of injection devices. One such factor is the size of the device. The injection device may be sized to house the various drive components, yet a large device may reduce the portability for the user. Another factor that may affect the design of an injection device is the convenience to the user. For example, some injection devices are designed with a complicated or sophisticated user interface that requires a certain degree of learning as to how to set a dose, how to administer the set dose, and then how to reset the device after dose administration. Indeed, a number of injection device components can impact the overall size and portability of an injection device and therefore can impact convenience to the user.
There is, therefore, a general need for an injection device that can be quickly and easily used by a typical patient for self administration of such drugs, such as insulin or human growth hormones. In addition, there is a general need to an injection device that can be quickly and easily used to administer at least one and perhaps multiple preset or predetermined doses. There is, therefore, a general need for an injection device that can quickly and easily administer a plurality of preset doses. With such an injection device, there is also a need for a device that can quickly and efficiently reset itself so that the device stands ready for the next dose administration. There is, therefore, a need for a compact and portable drug delivery device that can administer one or more preset devices and that does not include an intricate and complicated user interface for dose setting, for dose administration, and preparing the injection device for the next dose setting and dose administration procedures.
These and other advantages will become evident from the following more detailed description of the invention.